1. Field of the Invention
The present invention relates to an apparatus for grinding spherical objects into an exact spherical shape.
2. Related Arts
Semiconductor wafers are subjected to a series of proceedings to inscribe circuit patterns on their surfaces, and then, each semiconductor wafer is diced to provide many IC or LSI chips for use in a variety of electronic devices.
The manufacturing of such IC or LSI chips, however, is apt to encounter following problems:
(1) Wafers are sliced out of silicon ingots to be subjected to grinding, polishing, dicing and other machining processes. Almost all final products thus provided, however, are found to be defective, and only one percent of the final products is found to be permissible. Accordingly the yield rate relative to the raw material is surprisingly low.
(2) Transportation and machining of semiconductor wafers must be effected in the perfect dust-free condition. Installation of clean rooms, however, cost too much.
(3) Slicing machines, polishing apparatuses, diffusing furnaces, grinding apparatuses, steppers, dicing machines and other machines and apparatuses are used at each manufacturing step. These machines and apparatuses, however, can be used exclusively for one particular size of wafers, and must be changed for handling different sizes of wafers. Replacement, however, is inhibitively expensive;
(4) Semiconductor wafers are very thin and fragile.
In the hope of reducing all of these problems it has been proposed that blocks of semiconductor material be machined to provide a lot of spherical bodies and that circuit patterns be inscribed on the surface of each ball-shaped semiconductor body; the spherical shape is physically stable, and is effectively resistive to deformation, breaking or damage.
The practice of the proposed method requires use of an apparatus for reshaping and ball-shaped semiconductor bodies into an exact spherical shape.
To meet this demand an apparatus for reshaping spherical objects into an exact spherical shape according to the present invention comprises at least a grinding section equipped with means for grinding spherical objects, an inlet section equipped with means for feeding spherical objects to the grinding section and an outlet section equipped with means for taking out spherical objects from the grinding section, said inlet section, grinding section and outlet section communicating by transporting means.
The transporting means may comprise an endless carrier belt having a series of apertures made for accepting spherical objects and a drive for driving the endless carrier belt, and the means for grinding spherical objects may comprise an endless grinding belt running parallel with the endless carrier belt in same or counter direction relative to the endless carrier belt at such a speed that causes spherical objects to rub on the endless grinding belt on account of the relative speed difference between the grinding and carrier belts, a flat support for supporting slidably the grinding belt, and a randomizer capable of reciprocating across the endless carrier and grinding belts to sandwich spherical objects between the randomizer and the endless grinding belt, thereby assuring the deviation-free grinding of spherical objects.
Selected apertures of the endless carrier belt are loaded with spherical objects one by one, and the endless grinding belt may have a longitudinal sphere-reshaping groove made on its center line, the cross-section of the longitudinal groove having the precise arc shape of the exact spherical shape, thereby giving the exact spherical shape to the spherical objects partly fitted in the longitudinal groove.
The inlet section may include means for putting spherical objects in each and every aperture of the endless carrier belt, and the outlet section may include means for sucking and taking out spherical objects from each and every aperture of the endless carrier belt.
The endless grinding belt and the randomizer may have fine-pulverized grindstone stuck fast to their surfaces. The grinding section may include means for feeding fine-pulverized grindstone into the means for grinding spherical objects.
The spherical objects may be ball-shaped pieces of semiconductor material.
Other objects and advantages of the present invention will be understood from the following description of an apparatus for grinding spherical objects into an exact spherical shape according to one preferred embodiment of the present invention, which is shown in accompanying drawings.